This invention generally relates to brake device used in a vehicle. More particularly, the present invention pertains to a vacuum brake booster to assist brake operation for a vehicle.
A known brake booster for an automobile is disclosed in a U.S. Pat. No. 5,890,775 issued on Apr. 6, 1999. This brake booster includes a housing in which is defined a at least one pressure space, a movable wall disposed in the housing for movement in the forward and rearward directions with respect to the housing and for dividing the pressure space into a front chamber to be connected to a vacuum source of the automobile and a rear chamber selectively connected the front chamber and atmospheric pressure, and a power piston connected to the movable wall. An input member is disposed in the power piston and is movable in the forward and rearward direction with respect to the power piston by the operation of a brake operation device (e.g., a brake pedal). A valve mechanism includes a vacuum pressure valve connecting the rear chamber with the front chamber in response to the operation of the input member and an atmospheric pressure valve connecting the rear chamber with atmospheric pressure in response to the operation of the input member. An output member is movable in the forward direction in response to the movement of the power piston with the movable wall for outputting the forward movement force of the power piston to a driven device located outside the booster. An auxiliary movable wall is disposed in the front chamber and is movable in the forward and rearward directions, with the auxiliary movable wall moving the output member by engagement with the output member. A partition member is disposed in the front chamber and defines an auxiliary chamber between the front chamber and the auxiliary movable wall, and a valve controls communication of the auxiliary chamber with atmospheric pressure in an automobile compartment through the rear chamber or through a connecting pipe.
With this vacuum brake booster, the auxiliary chamber is connected to atmospheric pressure in the vehicle compartment through a connecting pipe by the valve. This structure requires a relatively complicated vehicle assembling step, which may reduce the operational or assembling efficiency associated with the brake booster. Further, this brake booster is a so-called high jump output type of brake booster which increases the output of the vacuum brake booster by operation of the auxiliary movable wall.
A need thus exists for a vacuum brake booster constructed in a way that improves the work efficiency associated with assembling the booster into the vehicle.
A need also exists for a vacuum brake booster capable of generating an output in response to the intent of the driver of the vehicle by increasing the output from the auxiliary movable wall of the booster in response to the input force.
According to the present invention, a vacuum brake booster includes a housing in which is provided at least one pressure chamber, a movable wall disposed in the housing and dividing the pressure chamber into a front chamber to be connected to a vacuum pressure source and a rear chamber selectively connected to the front chamber and atmospheric pressure, a power piston connected to the movable wall, an input member disposed in the power piston for movement in the front and rearward directions through operation of an operation member, and a valve mechanism having a vacuum valve connecting the rear chamber with the front chamber in response to the movement of the input member and an atmospheric pressure valve connecting the rear chamber to the atmospheric pressure in response to the movement of the input member. An output member outputs the forward force of the power piston by moving forward with the forward movement of the power piston in response to the movement of the movable wall, and an auxiliary movable wall is disposed in the front chamber and movable in forward and rearward directions. The auxiliary movable wall moves the output member through engagement with the output member. A partition member is disposed in the front chamber to define, with the auxiliary movable wall, an auxiliary chamber in the front chamber, with the rear chamber and the auxiliary chamber being connectable with each other.
The vacuum brake booster also includes a communication passage connecting the rear chamber and the auxiliary chamber, and a first valve disposed between the rear and auxiliary chambers for permitting or preventing fluid communication via the communication passage. The first valve selectively connects the auxiliary chamber with the vacuum pressure source or with the rear chamber. The first valve can be actuated in response to the vehicle condition to establish the communication between the auxiliary chamber and the rear chamber. The first valve can also be actuated by the operation of the driver of the vehicle to establish communication between the rear chamber and the auxiliary chamber.
The booster can also include a second valve located in the communication passage between the first valve and the rear chamber for establishing communication between the first valve and the rear chamber when the pressure in the rear chamber reaches a predetermined value. Communication between the first valve and the rear chamber can be established by the second valve when the pressure in the rear chamber reaches a predetermined value.
Vacuum Brake Booster for a Vehicle Comprising:
The present invention also provides a vacuum brake booster that includes a housing, a movable wall disposed in the housing for movement in forward and rearward directions and dividing the interior of the housing into a front chamber connectable to a vacuum pressure source and a rear chamber adapted to be selectively communicated with the front chamber and atmospheric pressure, a power piston connected to the movable wall and adapted to move in the forward directions through movement of the movable wall in the forward direction, an input member disposed in the power piston for movement in the forward and rearward directions according to operation of an operation member, and a valve mechanism that includes a vacuum valve adapted to selectively permit and prevent communication between the rear chamber and the front chamber in response to movement of the input member and an atmospheric pressure valve adapted to permit and prevent communication of the rear chamber with the atmospheric pressure in response to movement of the input member. An output member is adapted to move in the forward direction through movement of the power piston in the forward direction as a result of movement of the movable wall in the forward direction, and an auxiliary movable wall is disposed in the front chamber and movable in the forward and rearward directions. The auxiliary movable wall includes an engaging portion that engages a portion of the output member upon forward movement of the auxiliary movable wall to move the output member in response to movement of the auxiliary movable wall. A diaphragm is disposed in the front chamber and defines together with the auxiliary movable wall an auxiliary chamber in the front chamber. A mechanism is also provided for connecting the rear chamber with the auxiliary chamber.
According to another aspect of the invention, a vacuum brake booster includes a housing, a movable wall disposed in the housing for movement in forward and rearward directions and dividing the interior of the housing into a front chamber connectable to a vacuum pressure source and a rear chamber adapted to be selectively communicated with the front chamber and atmospheric pressure, a power piston connected to the movable wall and adapted to move in the forward directions through movement of the movable wall in the forward direction, an input member disposed in the power piston for movement in the forward and rearward directions according to operation of an operation member, and a valve mechanism that includes a vacuum valve adapted to selectively permit and prevent communication between the rear chamber and the front chamber in response to movement of the input member and an atmospheric pressure valve adapted to permit and prevent communication of the rear chamber with the atmospheric pressure in response to movement of the input member. An output member is adapted to move in the forward direction through movement of the power piston in the forward direction as a result of movement of the movable wall in the forward direction. An auxiliary chamber is disposed in the front chamber and is formed by a partition and a movable auxiliary wall. The auxiliary wall includes a portion which engages the output rod upon movement of the auxiliary wall in the forward direction, with the auxiliary wall being connected to the rear chamber to permit communication between the auxiliary chamber and the rear chamber.